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Professor Mark Post claims his stem cell burger could hold the solution to growing global meat demand. He explained how his scientists are trying to achieve that final elusive lab result – making it something people want to eat.

The nineteenth-century doom-laden Malthusian prophecy of global starvation due to population growth has still not come to pass. But today there is a major factor impacting world food supplies, and that is our nigh universal love for meat. Around 70% of arable farmland is dedicated to crops, not for human consumption, but to feed the cattle we serve up as steaks, sausages, mincemeat, burgers, kebabs…. To produce 15g of meat, an animal must be fed 100g of vegetables. That is not an efficient productivity ratio.

And because of the growing demand for meat in emerging market diets, the proportion of arable land used to feed these animals is on course to increase. The diet in developing economies is approaching the west’s trophic level of 2.3 (where a completely carnivorous individual would have a trophic level of 3, and a vegetarian one of 2). Some experts claim that at current rates of expansion, by 2050 all the world’s crops will be needed just to sustain production of the world’s meat products.

The solution coined by Mark Post, of the Department of Physiology at Maastricht University in the Netherlands, was to grow animal tissue using muscle stem cells. Stem cells are the components of body tissues that can differentiate to grow and replace damaged cells very fast. Every vertebrate has these stem cells in their muscle tissue.

Stem cells grow very, very fast. Given the right nourishment and environmental conditions, they double 35 times. One muscle extract obtained through a biopsy from a live animal can yield 10,000kg of meat. After differentiation, they merge to form a smooth wall of muscle. Still, the scale at which this growth occurs is small. The resulting rings of muscle cells are just 2.5cm long and 1mm in diameter. Further expansion is difficult, because they have no blood vessels to transport nutrients to cells in the centre.

This is an area Post is keen to explore, and sees two possible solutions: either an “artificial channel system to mimic the blood vessel system”, or to grow a biological blood transport system, complete with tiny capillaries. It seems this could necessitate an artificial pump, but he suggested that “stimuli coming from the interior cells that drive growth and repair” could be sufficient to direct the flow of nutrients. His ultimate goal, he said, was to create an authentic T-bone steak, – without harming any animals in the process.

Post claimed his original idea was to make a sausage and “present it to the audience while the pig was running around honking.” But after he presented the proposal to Google founder Larry Page, his new patron insisted as a condition of his support that it was a burger, rather than a sausage, as Post had first envisioned.

“I wanted to produce a sausage, and present it to the audience while the pig was running around honking.” (Mark Post, Maastricht University)

Another way the professor proposes to enhance the technology is through tailoring the proteins and amino acids the meat contains. He states that in future, they might remove harmful proteins such as those which cause colon cancer. And that they would incorporate fat cells, which would serve the dual purpose of making the burger juicier, and of improving its nutritional content: the fatty acids, when separated from their respective glycerol molecule, are essential for bodily functions including steroid synthesis, and in the phospolipid bilayer which forms a part of the plasma membrane in all body cells.

Fun Fact:

A number of other important biological molecules are also lipids. Vitamins A, E and K are terpenes, compounds similar to steroids but somewhat smaller. Steroids, of which Vitamin D and cholesterol are two examples, are lipids consisting of four interlinked rings of carbon atoms. Other important steroids are derived from cholesterol, among them the sex hormones progesterone and testosterone, and the hormone aldosterone secreted by the adrenal cortex. Bile salts, such as glycocholate and taurocholate, are polar metabolic products of cholesterol necessary for functioning digestion of lipids.

Here comes the science…

Tests have been conducted as to the ideal solution to promote adipogenesis, adipose or fat stem cell replication. Post cites Lin et al, ‘Tissue Engineering A,’ 2011, as having demonstrated the effectiveness of ADSC in collagen gel for this purpose. The expression of fatty acids Rosi, Phytanic and Linoleic acids were especially boosted, and to a lesser extent myristoleic and elaidic acids.

The optimum condition to enlarge and increase muscle cells is achieved through subjecting them to tension (“Muscle cells are exercise junkies,” says Post), so stretching them between two points gives them an effective workout that could also increase the muscle mass. It has been found that electrical currents stimulate muscle activity, but over time this wears them out rather than building them up.

In addition, the team is experimenting with the solutions it will use on the muscle tissue as it is being incubated. By coating the cells with a substance such as Matrigel, at a concentration of 1:200, you create an immersive 3D culture environment. In contrast, a petri dish donates nutrition via a flat, 2D surface. Matrigel was the most effective coatings tested, causing the highest relative expression of stem cells. Other coatings trialled in the experiment were laminine (concentration 1:10) and biolaminine (concentration 1:25).

A potential obstacle to sustainability is that, in addition to the original biopsy, calve serum is used to deliver vital nutrients. Eventually if cultivation of muscle cells can be scaled up, it would be possible to grow new cell populations out of cells already synthesised in the laboratory. But to maintain a supply of calve serum would necessitate diverse herds of livestock; something Post wants to phase out, as an inefficient use of land and corn. They have had promising results with a few non-serum media.*[1]

The first three stem cell burgers were served up live on TV last August to notable food critics, author Josh Schonwald and Hanni Ruetzler of Future Food Studio, who gave the home-grown dish what Post calls a polite but honest reception. The cost of this particular menu item was in total €250,000 in equipment, materials and labour. In order to make the process efficient and cost-effective, the team would have to expand production to a commercial scale. The task of modelling how to achieve this was contracted to J.Rowley, allegedly the world’s largest supplier of stem cells for laboratory purposes.

J. Rowley’s model did not account for all the further enhancements envisioned for the process. It made a number of technical assumptions: that 52 population doublings were possible; that the achievable cell concentration in the microcarrier culture would be 7.0e6 cells/ml; and the microcarrier concentration 10g/L. Consultants at J.Rowley mapped out a method by which cells were conveyed from plates to flasks, to a cell factory to a cell culture, via a mixing facility to a filling facility, and culminating in a discrete freeze drier. The final cost per kg of beef production? An average of $65.57, which at current exchange rates is £39.33. At the current retail price of meat, this seems on a par with livestock farmed the traditional way.

The headline figure is that a single bioreactor, incorporating 13 cycles per year, could feed a population of 10595. Each batch of cells yielded by the chain of production would yield 35000kg of meat, without endangering the life of a single cow.

That’s 175,000,000,000,000 individual, artificially synthesised cells, for those of you who are impressed by big numbers.

And why stop there? Post jokingly hypothesised about the creation of ‘animal hybrids’, meat containing components for two or more different species. Pick and Mix…He theorised that technically, it would be possible for people to grow meat at home in domestic incubators, provided they tended their incubator with the same care and patience as a garden or allotment.

Hey, it sounds fantastical. But five years ago, what would you have said in response to someone who claimed they could ‘grow meat’?

[1] If you are interested, results for the solution 6% Xerum free + Mix +1% P/S/A ingevoren aliquots suggested it could be a viable alternative.

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